SparkNotes cites two main themes apparent in "An Occurrence at Owl Creek Bridge": the fluid nature of time and the blurred line between reality and illusion. The short fiction piece by Ambrose Bierce tells the story of the hanging of secessionist farmer Peyton Farquhar.
From the moment Farquhar steps off the bridge from which he is being hanged to the moment of his death, time slows down, and the narration takes the reader on a journey of escape that only happens in the mind of the doomed farmer. The sense of time portrayed in the story is fluid and moves with the moments in the story. The lines of reality are blurred, as well. Farquhar goes to an alternate place and time where the events he is perceiving feel real but are not actually happening.